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A model for variations in single and repeated egg counts in schistosoma mansoni infections

Published online by Cambridge University Press:  06 April 2009

S. J. De Vlas ,
B. Gryseels ,
G. J. Van Oortmarssen ,
A. M. Polderman  and
J. D. F. Habbema
S. J. De Vlas
Affiliation:
Department of Public Health and Social Medicine, Medical Faculty, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
B. Gryseels
Affiliation:
Laboratory of Parasitology, Faculty of Medicine, University of Leiden, P.O. Box 9605, 2300 RC Leiden, The Netherlands
G. J. Van Oortmarssen
Affiliation:
Department of Public Health and Social Medicine, Medical Faculty, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
A. M. Polderman
Affiliation:
Laboratory of Parasitology, Faculty of Medicine, University of Leiden, P.O. Box 9605, 2300 RC Leiden, The Netherlands
J. D. F. Habbema
Affiliation:
Department of Public Health and Social Medicine, Medical Faculty, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
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Extract

Faecal egg counts are often used to measure Schistosoma mansoni infection, but the considerable variation between successive counts complicates their interpretation. The stochastic model described in this paper gives a description of observed egg counts in a population and can be used as a tool to gain an insight into the underlying worm load distribution. The model distinguishes between two sources of variation in egg counts: (1) variation caused by the difference in worm load between individuals, and (2) the variability of egg counts for an individual with a given worm load. Empirical data, single and repeated measurements, from surveys in five villages in Burundi and Zaire have been used to fit and validate the model. We have discussed possible mechanisms that explain the differences in estimated values between the villages. The model indicates that the expected number of eggs in a stool sample per S. mansoni worm pair is lower than suggested by autopsy data and that, possibly as a consequence of immunity, the inter-individual variation in worm loads decreases with age.

Keywords

Schistosoma mansoniegg countsworm load distributionsstochastic model
Type
Research Article
Information
Parasitology , Volume 104 , Issue 3 , June 1992 , pp. 451 - 460
Copyright
Copyright © Cambridge University Press 1992

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References

Anderson, R. M. & May, R. M. (1985). Helminth infections of humans: mathematical models, population dynamics, and control. In Advances in Parasitology, Vol. 24 (ed. Baker, J. R. & Muller, R.), pp. 1–101. London: Academic Press.Google Scholar
Barreto, M. L., Silva, J. T. F., Mott, K. E. & Lehman, J. S. (1978). Stability of faecal egg excretion in Schistosoma mansoni infection. Transactions of the Royal Society of Tropical Medicine and Hygiene 72, 181–7.CrossRefGoogle ScholarPubMed
Bradley, D. J. (1972). Regulation of parasite populations: a general theory of the epidemiology and control of parasitic infections. Transactions of the Royal Society of Tropical Medicine and Hygiene 66, 697–708.CrossRefGoogle ScholarPubMed
Bradley, D. J. & May, R. M. (1978). Consequences of helminth aggregation for the dynamics of schistosomiasis. Transactions of the Royal Society of Tropical Medicine and Hygiene 72, 262–73.CrossRefGoogle ScholarPubMed
Brooks, F. P. (1985). Gastrointestinal system. In Best and Taylor's Physiological Basis of Medical Practice, 11th Edn (ed. West, J. B.), pp. 634–790. Baltimore: Williams & Wilkins.Google Scholar
Butterworth, A. E., Capron, M., Cordingley, J. S., Dalton, P. R., Dunne, D. W., Kariuki, H. C., Kimani, G., Koech, D., Mugambi, M., Ouma, J. H., Prentice, M. A., Richardson, B. A., Arap Siongok, T. K., Sturrock, R. F. & Taylor, D. W. (1985). Immunity after treatment of human schistosomiasis mansoni. II. Identification of resistant individuals, and analysis of their immune responses. Transactions of the Royal Society of Tropical Medicine and Hygiene 79, 393–408.CrossRefGoogle ScholarPubMed
Cheever, A. W. (1968). A quantitative post-mortem study of schistosomiasis mansoni in man. American Journal of Tropical Medicine and Hygiene 17, 38–64.CrossRefGoogle ScholarPubMed
Cheever, A. W., Kamel, I. A., Elwi, A. M., Mosimann, J. E. & Danner, R. (1977). Schistosoma mansoni and S. haematobium infections in Eygpt II. Quantitative parasitological findings at necropsy. American Journal of Tropical Medicine and Hygiene 26, 702–16.CrossRefGoogle Scholar
Chen, M. G. & Mott, K. E. (1988). Progress in assessment of morbidity due to Schistosoma mansoni infection. Tropical Diseases Bulletin 85, R1–R56.Google Scholar
Cox, D. R. & Hinkley, D. V. (1974). Theoretical Statistics. London: Chapman and Hall.CrossRefGoogle Scholar
Davenport, H. W. (1961). Physiology of the Digestive Tract. Chicago: Year Book Medical Publishers Incorporated.Google Scholar
Gryseels, B. (1988). The morbidity of schistosomiasis mansoni in the Rusizi Plain (Burundi). Transactions of the Royal Society of Tropical Medicine and Hygiene 82, 582–7.CrossRefGoogle ScholarPubMed
Gryseels, B. & Nkulikyinka, L. (1988). The distribution of Schistosoma mansoni in the Rusizi Plain (Burundi). Annals of Tropical Medicine and Parasitology 82, 581–90.CrossRefGoogle ScholarPubMed
Gryseels, B. & Polderman, A. M. (1987). The morbidity of schistosomiasis mansoni in Maniema (Zaire). Transactions of the Royal Society of Tropical Medicine and Hygiene 81, 202–9.CrossRefGoogle ScholarPubMed
Gryseels, B. & Polderman, A. M. (1991). Morbidity and morbidity control of schistosomiasis mansoni in Subsaharan Africa. Parasitology Today 7, 244–8.CrossRefGoogle ScholarPubMed
Gryseels, B., Nkulikyinka, L. & Engels, D. (1991). Repeated community-based chemotherapy for the control of Schistosoma mansoni: effect of screening and selective treatment on prevalences and intensities of infection. American Journal of Tropical Medicine and Hygiene 45, 509–17.CrossRefGoogle ScholarPubMed
Hall, A. (1982). Intestinal helminths of man: the interpretation of egg counts. Parasitology 85, 605–13.CrossRefGoogle ScholarPubMed
Johnson, N. L. & Kotz, S. (1969). Discrete Distributions. Boston: Houghton Mifflin Company.Google Scholar
Katz, N., Chaves, A. & Pellegrino, J. (1972). A simple device for quantitative stool thick-smear technique in schistomiasis mansoni. Revista do Instituto de Medicina Tropical de Sao Paulo 14, 397–400.Google Scholar
Loker, E. S. (1983). A comparative study of the life-histories of mammalian schistosomes. Parasitology 87, 343–69.CrossRefGoogle ScholarPubMed
Macdonald, G. (1965). The dynamics of helminth infections, with special reference to schistosomes. Transactions of the Royal Society of Tropical Medicine and Hygiene 59, 489–506.CrossRefGoogle ScholarPubMed
May, R. M. (1977). Togetherness among schistosomes: its effects on the dynamics of the infection. Mathematical Biosciences 35, 301–43.CrossRefGoogle Scholar
Medley, G. & Anderson, R. M. (1985). Density-dependent fecundity in Schistosoma mansoni infections in man. Transactions of the Royal Society of Tropical Medicine and Hygiene 79, 532–4.CrossRefGoogle ScholarPubMed
Nasell, I. & Hirsch, W. M. (1973). The transmission dynamics of schistosomiasis. Communications on Pure and Applied Mathematics 26, 395–453.CrossRefGoogle Scholar
Polderman, A. M. (1979). Transmission dynamics of endemic schistosomiasis. Tropical and Geographical Medicine 31, 465–75.Google ScholarPubMed
Polderman, A. M. & De Caluwe, P. (1989). Eight years of targeted mass treatment of Schistosoma mansoni infection in Maniema, Zaire. Tropical Medicine and Parasitology 40, 177–80.Google ScholarPubMed
Polderman, A. M., Kayiteshonga, Mpamila, Manshande, J. P. & Bouwhuis-Hoogerwerf, M. L. (1985). Methodology and interpretation of parasitological surveillance of intestinal schistosomiasis in Maniema, Kivu Province, Zaire. Annales de la Société Belge de Médecine Tropicale 65, 243–9.Google ScholarPubMed
Press, W. H., Flannery, B. P., Teukolsky, S. A. & Vetterling, W. T. (1990). Numerical Recipes, The Art of Scientific Computing. Cambridge: Cambridge University Press.Google Scholar
Sakamoto, Y., Ishiguro, M. & Kitagawa, G. (1986). Akaike Information Criterion Statistics. Tokyo: KTK Scientific Publishers.Google Scholar
Teesdale, C. H., Fahringer, K. & Chitsulo, L. (1985). Egg count variability and sensitivity of a thin smear technique for the diagnosis of schistosomiasis mansoni. Transactions of the Royal Society of Tropical Medicine and Hygiene 79, 369–73.CrossRefGoogle Scholar
Warren, K. S. (1973). Regulation of the prevalence and intensity of schistomiasis in man: immunology or ecology? Journal of Infectious Diseases 127, 595–609.CrossRefGoogle ScholarPubMed
Wertheimer, S. P., Vermund, S. H., Lumey, L. H. & Singer, B. (1987). Lack of demonstrable density-dependent fecundity of schistomiasis mansoni: analysis of Egyptian quantitative human autopsies. American Journal of Tropical Medicine and Hygiene 37, 79–84.CrossRefGoogle Scholar
World Health Organization (1985). The Control of Schistomiasis: Report of a WHO Expert Committee. Geneva: World Health Organization (Technical Report Series, No. 728).Google Scholar
Wilkins, H. A. (1987). The epidemiology of schistosome infections in man. In The Biology of Schistosomes: From Genes to Latrines (ed. Rollinson, D. & Simpson, A. J. G.), pp. 379–97. London: Academic Press.Google Scholar